standard Form Validation for textareas

This is what I have come up with.. seems to work:

PHP Code:

if ( ! function_exists('customAlpha')) {
    function customAlpha($str)
    {
        if (!preg_match('/^[a-zA-Z0-9 .,\-\']*$/m', $str)) {
            return FALSE;
        } else {
            return TRUE;
        }
    }
}